Microplastic accumulation on urban footpaths: microplastic deposition on concrete and asphalt surfaces after a single running event

Microplastics pose environmental and health threats worldwide because of their ubiquity, small size, toxicity and detrimental effects to organisms and ecosystem function. Previous research in wilderness areas has found that trail running releases microplastics due to abrasion of synthetic clothing and footwear. However, there is limited information regarding microplastic deposition due to regular running events on urban footpaths, which could spread to surrounding areas and contaminate the environment. This study assessed the abundance of microplastics on two types of surfaces (concrete versus asphalt) and slopes (flat versus slope) in relation to a weekly running event, the globally recognized and popular Parkrun. Samples were collected before and after a Parkrun event using forensic gel lifter tape. Small fibers had very low occurrence in samples with no depositional patterns evident. Microplastic particles displayed strong depositional patterns that indicated a 'ceiling' to surface accrual as well as measurable deposition after one Parkrun event. Patterns of deposition were higher in areas on sloped surfaces, and partially higher on rougher surfaces, although landscape position was likely a confounding factor in surface type response. Further studies to investigate microplastic mobility and accumulation over time, as well as the effects of wind or sampling efficiencies, are needed to quantify potential environmental impacts after such regular running events, and on footpaths and small trails and tracks in general.